Ball-screw assemblies are well-known, and are widely used in linear motion translation applications. Heretofore, ball recirculation paths have been built into the nut. This requires the screw to have a fully-threaded length to meet the linear translation stroke requirements. As a result of this, exposure of the threaded portion to the load will contribute to the screw becoming contaminated or damaged in a harsh working environment. This will eventually reduce service capacity and service life.
Alternatively, additional arrangements, such as an extra rod tube or a flexible cover attachment, have been used to protect the thread portion from such contamination.
The most common electrically-powered linear devices include an electric motor packaged with a linear motion device, such as a lead screw, ball-screw or planetary roller screws.
Examples of prior art actuators of this general type are representatively shown and described in U.S. Pat. Nos. 3,660,704, 5,041,748, 5,391,953, 5,491,372 and 5,557,154.
Accordingly, it would be generally desirable to provide an improved reverse transfer system ball-screw arrangement in which the screw threads are protected from unnecessary exposure to a harsh environment.